Patent GB-664538-A (GB)
Title: Improvements relating to apparatus for scanning cinematograph films for the purpose of generating television signals or recording television pictures
Inventor: HOLMAN HERBERT EDWARD
IPC: H04N3/38
Filed: 1949-04-07
Abstract: 664,538. Television. ELECTRIC & MUSICAL INDUSTRIES, Ltd. March 22, 1950 [April 7, 1949], No. 9462/49. Class 40 (iii). Television apparatus for scanning cinematograph film for the purpose of generating television signals or recording television images comprises means for enabling the apparatus to co-operate with either continuously moving film as described in Specification 475,032 or stationary film. A rotatable shutter, Fig. 2, is formed with a plurality of angularly-spaced apertures, means being provided for adjusting the angular extent of the apertures according as to whether the film is moving or stationary. Fig. 1 shows the apparatus set for scanning of continuously-moving film. A scanning raster, or a reproduced picture, is produced upon the screen of the cathode-ray tube 1 with the vertical scanning amplitude decreased to half its normal amplitude so that the aspect ratio of the raster or picture is twice the usual value. Twin optical systems 13 and 14 project images of the raster or picture spaced apart by half the height of one frame of the film on to the film 8, each image having a height equal to half that of the film frame. The shutter 15 is rotated in synchronism with the motion of the film, which is drawn downwards by the action of sprocket 10, and with the scanning of the cathode-ray beam in tube 1 so that the images produced by lens 13 and 14 are alternately exposed and by virtue of the motion of the film interlace to provide interlaced scanning of the film. The shutter 15 comprises two coaxially mounted discs 16 and 17 having vanes 29 and 30 respectively which in the arrangement as shown are so spaced that the shutter comprises vanes and apertures of equal height, each approximately equal to half the film-frame height. When it is desired to scan stationary film, the driving motor for the sprocket 10 and shutter 15 is stopped and a switch 45 is operated. The operation of switch 45 changes the amplitude of the frame-scanning waveform for tube 1 to provide the normal aspect ratio and also operates an electromagnet 44 which through mechanical linkages lifts a shutter 51 to obstruct the lens 14 and operates upon shutter 15 to rotate the portions 16 and 17 so that the vanes 29 and 30 register with one another. The aperture between the vanes of the shutter is thus increased to a sufficient value to allow the image, projected by lens 13 and having the normal aspect ratio, to pass to the film. A manual control is provided to allow for adjustment of the position of the shutter. A further electromagnet 62 is also operated by switch 45 to apply a brake pad 60 to the disc 58 of a centrifugal governor driven from the following film sprocket 9. The sprocket 10 may be rotated manually to select a desired film frame, the contact between the pad 60 and disc 58 holding the film taut. In an alternative arrangement the switch 45 may also control the film driving motor. Furthermore the discs 16 and 17 may be spring-loaded and operated centrifugally so that when the shutter rotates the vanes take up the position shown in Fig. 2.